High Excess Research Articles

Electrochemical Characterization of Low-Temperature Direct Ethanol Fuel Cells using Direct and Alternate Current Methods

Here, we report for the first time the results of systematic characterization of a low-temperature polymer electrolyte membrane direct ethanol fuel cell using DC and AC electrochemical methods. Model catalysts (carbon supported Pt nanoparticles) painted on carbon paper are used as anode and cathode. Influence of physical parameters, such as cell temperature, current density, and ethanol concentration, and anode fuel flow rate on overall cell impedance is studied. Analysis of the obtained impedance spectra in connection with DC measurements allows us to comment on cell properties and to separate different contributions to the overall cell polarization. Our results suggest that the cell impedance is dominated by anode faradaic impedance, with a small or negligible contribution from cathode faradaic impedance. The anode impedance depends strongly on current density and cell temperature, but is not significantly influenced by ethanol concentration. Presence of anode mass-transfer impedance, even when ethanol was fed to the cell in high excess, is confirmed. Based on the results, we conclude that changes in ethanol electro-oxidation mechanism might manifest themselves on the impedance spectra in the low-frequency inductive loop. Nonetheless, further studies involving equivalent circuit modelling are needed to determine the exact influence of the cell parameters on the anode kinetics.Graphical

Quaternization of algal/PEI beads (a new sorbent): Characterization and application to scandium sorption from aqueous solutions

Algal/Polyethyleneimine beads (APEI) were successfully quaternized to prepare an efficient sorbent (Q-APEI) for Sc(III) recovery. The functionalization has been confirmed by a series of analytical procedures: titration (pHPZC), elemental analysis, SEM, BET, EDX, FTIR, XPS and TGA. The sorption properties for Sc(III) from mild acidic solutions have been compared for APEI and Q-APEI: the sorption capacity increases from 1.0 to 3.8 mmol Sc g−1, at the optimum pH; (i.e., 4.5). The porous structure (specific surface area close to 34 m2 g−1) of the sorbent allows reaching the equilibrium within 60–90 min. Metal desorption is highly efficient using 0.5 M HCl/CaCl2 solutions; the sorbent can be recycled for at least 5 cycles with limited decrease in sorption capacity. FTIR and XPS analysis confirm the stability of the material though some chemical changes can be observed. The sorption mechanism involves different reactive groups associated with the diversity of functional sites: carboxylate groups (from alginate) and more specifically amine groups (from PEI and quaternary amine grafted moieties) with contribution of different scandium species (free or scandium sulfate complexes), depending on the pH. The sorbent is selective from Mg(II), Sm(III), Ca(II) and Na(I) (from equimolar synthetic solutions) at pH higher than 4. The application of Q-APEI for the sorption of Sc(III) from industrial solution (derived from red mud) shows that despite a high excess of iron, titanium or aluminum, scandium sorption is highly efficient (even at low metal concentration); though the sorbent is not selective.

A pilot study of family-based management of behavioral excesses in young Iranian children with autism spectrum disorder.

Parent-mediated early behavioral interventions are considered as effective approaches in the treatment of children with Autism Spectrum Disorder (ASD). The majority of these interventions focus on social-communication deficits rather than behavioral excesses which severely irrupt child and family social life as well as the child's appearance behavior and learning processes. The study examines the effectiveness and feasibility of Family-based Management of Behavioral Excesses of Autism Program (FMBEAP) on Iranian families. This pre-post and follow-up intervention study involved 17 parents of children with DSM-5 diagnosis of ASD recruited from Tehran Autism Center. All parents conducted FMBEAP on their children while receiving 10-weekly group supervision on top of everyday on-line individual coaching. The study's measures were Repetitive Behavior Scale-R, video-monitoring of child-parent Interaction, Clinical Global Impression-Improvement Scale, Parental Self-Efficacy and Parenting Stress Index-short form. The measures were applied to the sample three times: pre and post-intervention and at one-month follow-up. The Results showed high and low order behavioral excesses significantly decreased at post-intervention and the follow-up. 15 out of 17 children reached to recovered or highly recovered at post-test. Parents showed significant improvements in self-efficacy and parenting stress scales. The intervention was highly accepted by them. FMBEAP is shown to be a feasible, acceptable and effective intervention to improve autistic behavioral. The parents should also benefit from the program in terms of self-efficacy and parenting stress. FMBEAP is highly recommended for overcoming behavioral excesses along with those interventions focus on behavioral deficits in ASD.

Initial characterization of interstellar comet 2I/Borisov

Interstellar comets penetrating through the Solar System had been anticipated for decades. The discovery of asteroidal-looking 'Oumuamua was thus a huge surprise and a puzzle. Furthermore, the physical properties of the 'first scout' turned out to be impossible to reconcile with Solar System objects, challenging our view of interstellar minor bodies. Here, we report the identification and early characterization of a new interstellar object, which has an evidently cometary appearance. The body was discovered by Gennady Borisov on 30 August 2019 UT and subsequently identified as hyperbolic by our data mining code in publicly available astrometric data. The initial orbital solution implies a very high hyperbolic excess speed of ~32 km/s, consistent with 'Oumuamua and theoretical predictions. Images taken on 10 and 13 September 2019 UT with the William Herschel Telescope and Gemini North Telescope show an extended coma and a faint, broad tail. We measure a slightly reddish colour with a g'-r' colour index of 0.66 +/- 0.01 mag, compatible with Solar System comets. The observed morphology is also unremarkable and best explained by dust with a power-law size-distribution index of -3.7 +/- 1.8 and a low ejection speed (44 +/- 14 m/s for $\beta$ = 1 particles, where $\beta$ is the ratio of the solar gravitational attraction to the solar radiation pressure). The nucleus is probably ~1 km in radius, again a common value among Solar System comets, and has a negligible chance of experiencing rotational disruption. Based on these early characteristics, and putting its hyperbolic orbit aside, 2I/Borisov appears indistinguishable from the native Solar System comets.

Intra-landscape distribution of snow storage in the Mayma river basin (low-mountain area of the Russian Altai)

The paper presents the results of observations and cartographic modeling of distribution of maximum snow storages (snowpack water equivalent) in the low-mountain forest landscapes of the Maima river basin in different by snow amount winters. The weather conditions during cold periods of 2014/15-2017/18 were analyzed. The data on precipitation and mean monthly temperatures for the above mentioned seasons were compared with averaged values for 1998-2018 as the whole. It was found that the values of snow storages as well as losses for evaporation here are mainly conditioned by the meteorological parameters of the cold period. The algorithm of mapping with the use of the landscape cartographic basis and corrections for features of the relief and the character of the underlying surface is proposed. This algorithm may be used in the studies of snow accumulation in low-mountain forest landscapes. It had been found that the cold periods of 2014/15 and 2016/17 were characterized by the highest excess of winter precipitation over the averaged long-term values, whereas the lowest values were typical for 2017/18 and 2015/16. According to mean monthly air temperatures, the investigated winters were warm. The data on the in situ measurements and calculations confirm the dependence of snow accumulation in the basin on an altitude gradient, vegetation features, expositions and surface steepness. Consistently high values of snow storages are characteristic for the black-taiga landscapes on the shadow slopes (North-Western, Northern and North-Eastern expositions) with an angle of up to 20° with small-leaved forests. Minimum values of snow storages are observed in the sub-taiga part of the basin on the slopes of light (South-Western, Southern and South-Eastern) and transitional (Western and Eastern) expositions with an angle of more than 20° with the domination of original coniferous forests.

Effect of Sheet Pile Driving on Geotechnical Behavior of Adjacent Building in Sand: Numerical Study

Construction vibration such as sheet pile driving can produce earthborn vibrations which may be leads to problems for the supporting soils and adjacent structures. Vibrations create the stress waves traveling outward from the source through the soil and cause structural damage due to dynamic vibration induced settlement. The main aim of the present research is to study the vibration effect through sheet pile driving technique on the surrounding soil and adjacent structure. A series of plain strain finite element analysis using Plaxis 8.2 dynamic module is run to simulate the installation technique of a sheet pile unit using driving technique (hammer type). The effect of construction stages with different embedded sheet pile depth, sand relative density, and foundation distance from the driving source is also studied. The influence of hammer driving amplitude on the foundation response and excess pore water pressure are presented. The results showed that the increase of both embedment sheet pile depth and hammer efficiency can significantly produce higher excess pore water pressure and foundation settlement. The increase of sand density can also has a great effect in increasing the foundation damage of adjacent structure compared with low sand relative density. The building damage can significantly take place when the driving is closed to foundation.

Skewed Kotz Distribution with Application to Financial Stock Returns

This paper introduced a five-parameter skewed Kotz (SK) distribution that may be viewed as a generalized skewed T distribution. Its mathematical properties are investigated, and parameters are estimated using the maximum likelihood method. The usefulness of this new distribution has been illustrated by deriving explicit formulae for the value-at-risk (VaR) and the average value-at-risk (AVaR). The obtained results are clearly generalizations of those that were established earlier by Dokov et al. (J Appl Funct Anal 3(1):189–208, 2008). On the other hand, simulation studies have been conducted and showed the accuracy of the VaR and AVaR computations. Furthermore, an application on financial returns of the Universal Health Services stock provided evidence that the SK distribution better fits the empirical distribution than both normal and skewed T distributions. The empirical study revealed the suitability of the SK distribution, specially for modelling data that fall within a small range, with a high excess kurtosis.

The hunt for the third acceptor in CuInSe2 and Cu(In,Ga)Se2 absorber layers

The model for intrinsic defects in Cu(In,Ga)Se2 semiconductor layers is still under debate for the full range between CuInSe2 and CuGaSe2. It is commonly agreed by theory and experiment, that there are at least one shallow donor and two shallow acceptors. Spatially resolved photoluminescence on CuGaSe2 previously revealed a third acceptor. In this study we show with the same method that the photoluminescence peak at 0.94 eV in CuInSe2, previously attributed to a third acceptor, is a phonon replica. However another pronounced peak at 0.9 eV is detected on polycrystalline CuInSe2 samples grown with high copper and selenium excess. Intensity and temperature dependent photoluminescence measurements reveal that this peak originates from a DA-transition from a shallow donor (<8 meV) into a shallow acceptor A3 (135 10) meV. The DA3 transition has three distinct phonon replicas with 28 meV spectral spacing and a Huang Rhys factor of 0.75. Complementary admittance measurements are dominated by one main step with an activation energy of 125 meV which corresponds well with the found A3 defect. The same defect is also observed in Cu(In,Ga)Se2 samples with low gallium content. For [Ga]/([Ga] + [In])-ratios of up to 0.15 both methods show a concordant increase of the activation energy with increasing gallium content shifting the defect deeper into the bandgap. The indium vacancy is discussed as a possible origin of the third acceptor level in CuInSe2 and in Cu(In,Ga)Se2.

Synergistic stabilisation of emulsions by blends of dairy and soluble pea proteins: Contribution of the interfacial composition

Proteins from animal and plant sources are known to be able to physically stabilise emulsions, whereas much less is known about emulsions prepared with blends of proteins of different origin. Here we use blends of pea protein isolate (PPI) with whey protein isolate (WPI) or with sodium caseinate (SC) to physically stabilise emulsions prepared by high pressure homogenisation. For both the blends and the individual proteins, droplet size, emulsion stability, surface load and interfacial compositions were determined. The d3,2 and surface load (measured over a concentration range 0.2–1.6 wt% protein in the starting aqueous solution) were the lowest for SC- and WPI-stabilised emulsions, and the highest for PPI-stabilised emulsions, whereas emulsions stabilised by the blends (1:1 ratio) had intermediate d3,2 values and surface loads. PPI- and SC-stabilised emulsions showed some physical destabilisation (e.g., flocculation and coalescence, respectively) over 14 days of storage, whereas the WPI-PPI or SC-PPI blends formed emulsions that remained stable, suggesting synergistic effects.When used in blends, both dairy and plant proteins adsorbed at the oil-water interface, but compositional rearrangements at the interface occurred within days. More specifically, whey proteins were able to partly displace pea proteins from the interface, which were themselves able to displace SC. However, such a displacement was only possible when the displacing protein was present in sufficiently high excess. Such considerations are usually not taken into account in food emulsion formulation, even though they are very relevant, as the interfacial layer protects emulsions droplets against physical destabilisation.

Genome-wide analysis indicates association between heterozygote advantage and healthy aging in humans

BackgroundGenetic diversity is known to confer survival advantage in many species across the tree of life. Here, we hypothesize that such pattern applies to humans as well and could be a result of higher fitness in individuals with higher genomic heterozygosity.ResultsWe use healthy aging as a proxy for better health and fitness, and observe greater heterozygosity in healthy-aged individuals. Specifically, we find that only common genetic variants show significantly higher excess of heterozygosity in the healthy-aged cohort. Lack of difference in heterozygosity for low-frequency variants or disease-associated variants excludes the possibility of compensation for deleterious recessive alleles as a mechanism. In addition, coding SNPs with the highest excess of heterozygosity in the healthy-aged cohort are enriched in genes involved in extracellular matrix and glycoproteins, a group of genes known to be under long-term balancing selection. We also find that individual heterozygosity rate is a significant predictor of electronic health record (EHR)-based estimates of 10-year survival probability in men but not in women, accounting for several factors including age and ethnicity.ConclusionsOur results demonstrate that the genomic heterozygosity is associated with human healthspan, and that the relationship between higher heterozygosity and healthy aging could be explained by heterozygote advantage. Further characterization of this relationship will have important implications in aging-associated disease risk prediction.

Genetic diversity of 10 indigenous chicken ecotypes from Southern Highlands of Tanzania based on Major Histocompatibility Complex-linked microsatellite LEI0258 marker typing

ABSTRACTUnraveling the genetic diversity of livestock species is central to understanding their value and importance for conservation and improvement in diverse production environments. In developing countries, information on genetic attributes of many livestock species is unfortunately scanty to support well-informed decision-making upon relevant management strategies. This study aimed at investigating allelic variability, genetic diversity, and genetic relationships of 10 indigenous chicken ecotypes from Southern Highlands of Tanzania using the Major Histocompatibility Complex-linked LEI0258 marker. A total of 400 DNA samples, 40 per ecotype, were genotyped by capillary electrophoresis. Thirty different alleles with sizes ranging from 197 to 569 bp were determined. The number of alleles ranged from 17 (Itunduma) to 21 (Mbeya), with an average of 19.20 alleles per ecotype. Allelic polymorphism was further evaluated through genotyping by Sanger sequencing. Thirty-three DNA samples with different fragment sizes were re-amplified and their alleles sequenced to depict polymorphism based on a combination of two repeat regions at 12 and 13 bp, respectively, and flanking regions with SNP and indels. The repeat region at 13 bp appeared 1 to 28 times, whereas the region at 12 bp appeared 3 to 19 times in all sequenced fragments. The numbers of indels and SNP determined were 7 and 9, respectively. From capillary electrophoresis, the Chunya and Msimbazi ecotypes exhibited the highest genetic diversity (0.937), whereas the lowest value (0.910) was observed from the Mbarali ecotype, with an average of 0.925. The Namtumbo and Wanging’ombe ecotypes showed high inbreeding coefficients (FIS > 0.05), whereas a high excess heterozygote value (FIS = –0.098) was observed from the Njombe ecotype. Two percent of the genetic diversity was due to differences among ecotypes, and the rest was due to differences among individuals within the ecotypes. Despite the overall low genetic differentiation, both fragment and sequencing analyses depicted a high allelic and genetic variability across 10 chicken ecotypes. These results therefore, underscore the importance of establishing appropriate conservation and management strategies to capitalize on observed variability and maintain genetic flexibility across diverse production environments.

Event‐Based Precipitation Isotopes in the Laurentian Great Lakes Region Reveal Spatiotemporal Patterns in Moisture Recycling

AbstractLake effect snowstorms influence climate, ecology, and agriculture in the Laurentian Great Lakes region and can be costly to surrounding communities in the United States and Canada. Stable isotopes of lake effect precipitation events throughout the year display a distinct signature that can be used to better understand how these storms may respond to a changing climate. Here we present event‐based δ18O and δ2H of precipitation from a site in Skaneateles, NY, downwind of Lakes Ontario and Erie, between April 2015 and February 2018. We find a seasonal isotopic cycle with a well‐defined signature of high deuterium excess (d‐excess) during National Weather Service‐defined lake effect snowstorms. Application of a previously developed moisture recycling model to this data set shows that up to 25% more moisture recycling takes place when the lake water and air temperature difference is large, air temperature is below freezing, and wind direction permits storms to move over Lake Ontario or Lake Erie. Moisture recycling occurs less frequently during spring, summer, and early fall due to meteorological and lake parameters that are less conducive to moisture recycling. Comparison of annual mean precipitation d‐excess at sites both upwind and downwind of the Laurentian Great Lakes provides evidence that this high d‐excess signature is characteristic of mean annual precipitation isotopic composition at downwind sites and therefore may be used to quantify changes in moisture recycling that occur on event to annual time scales in response to past and future climate changes.

Satellite-based analysis of landfill landslide: the case of the 2015 Shenzhen landslide

ABSTRACT With rapid urbanisation, the amount of construction solid waste is increasing, especially in developing countries, where landfill still dominates waste treatment. Lack of proper management and monitor, many landfills experience high landslide risk, and a typical case is the Guangming landfill landslide in Shenzhen, China on 20 December 2015. The main problem is that detailed field investigation for each landfill requires too much time and effort. Consequently, a satellite-based analysis method is identified and used to efficiently assess landslide susceptibility of landfill. The core steps include investigation of the topography and climate of the landfill site and dynamic evaluation based on satellite data. Taking the Guangming landfill as an example, rapid filling and water catchment are taken into account with GIS, which generate high excess pore pressures and eventually trigger the gentle landfill slope to failure. The results show that the satellite-based analysis method can obtain the key factors of the landfill landslide.

Case study of slope failure during construction of an open pit mine in Indonesia

This paper presents back-analyses of a failed slope at an open pit lignite mine in Muara Enim, Indonesia. The slope, which was being raised by the dumping of excavated material, failed at a dump height of 24 m, well before reaching the design height of 80 m. The primary cause of failure was determined to be the presence of a previously unknown weak layer in the foundation, combined with high excess pore pressures generated by a relatively fast dumping rate. The failure resulted in significant disruption of the mining operation, in addition to environmental problems and a high cost of remediation. Finite element analyses were performed to gain a better understanding of the influence of the weak layer at the time of the failure. The case history emphasizes the need for a thorough site investigation and the risks associated with fast dumping on saturated weak clay overlain by a stiff residual soil layer with low permeability.

Synthesis of α‐Alkyl‐β‐Hydroxy Amides through Biocatalytic Dynamic Kinetic Resolution Employing Alcohol Dehydrogenases

AbstractChiral (α‐substituted) β‐hydroxy amides are interesting derivatives as they are useful building blocks of many biologically active compounds. Herein, the biocatalytic stereocontrolled synthesis of various acyclic syn‐α‐alkyl‐β‐hydroxy amides through a dynamic kinetic resolution is shown. Hence, a series of overexpressed alcohol dehydrogenases (ADHs) in Escherichia coli was used to reduce the corresponding racemic β‐keto amides. Among them, ADH‐A from Rhodococcus ruber and commercial evo‐1.1.200 afforded the best activities and selectivities, giving access to the opposite enantiomers with high diastereomeric excess and excellent enantiomeric excess. Some of these compounds were obtained at semipreparative scale.magnified image

Heat-related morbidity: real-time surveillance via rescue service operations data from the interdisciplinary care capacity proof system (IVENA)

In addition to mortality data, hospital admission, emergency department visits, and emergency service calls data are used for the surveillance of heat-related morbidity. We report on heat-associated morbidity in Frankfurt am Main from 2014-2018 using the web-based care capacity proof system (IVENA) of the rescue service operations. In the web-based IVENA system, all patients with prehospital emergency care are recorded in real time. The rescue service operations were evaluated in the summer months (June-August) from 2014-2018 in Frankfurt am Main as awhole and separately according to various heat-related diagnoses. The current temperature data of the Frankfurt East measuring station were obtained online as hourly values from the website of the Hessian Institute for Nature Conservation, Environment and Geology ( www.hlnug.de ). Temperature maxima ≥32 ℃ for at least 5 days were defined as a "heatwave." From 2014-2018, three heatwaves occurred according to the definition above: in 2015, 2016, and 2018, with an extremely long heat period in 2018 (17days). During the heatwave in 2015, the highest excess morbidity was noted: +17% total ambulance service operations and +198% emergency service operations due to heat-related disease disorders. The evaluation of the long heat period in 2018 showed that with increasing duration of the heat period, the emergency rescue service operations due to total heat-associated morbidity remained high with increasing emergency service operations due to exsiccosis and unclear fever. The data obtained by the IVENA system enable acurrent and complete assessment of severe acute diseases in the city or in the respective rescue service area in real time. Health effects of heat events can thus be investigated in real time and the system can be used as an early warning system for prevention.

New Discoveries in Enantiomeric Separation of Racemic Tofisopam

Resolution process of tofisopam has been re-evaluated now based on our new investigations. Originally, it was carried out in the water-chloroform system, where the intermediate salt of high diastereomeric excess was described as (R)-TOF·(R,R)-DBTA·(H2O)3. Opposed to previous assumptions, we have actually found that a different solvate composition, (R)-TOF‐(R,R)-DBTA-CHCl3, forms with chloroform, in which molecules of CHCl3 are captured and held with different strengths. Moreover, resolution of TOF with (R,R)-DBTA is possible (and favourable) in water-free solvent and solvent mixture. However, presence of chloroform is essential, and thus, chloroform is also a suitable solvent alone. Among the tested solvents, toluene-chloroform mixture results in the highest resolution efficiency, while the highest enantiomeric purity was achieved when acetonitrile was in the system too. Resolution efficiency can be also increased by using the quasi-racemic resolving agent and thermodynamic control. Purification of enantiomeric mixtures was examined, and recrystallization of the diastereomeric salt was found to be the most efficient solution. Instructive behaviour of the complex enantiomer-conformer system of tofisopam is emphasized.

Unveiling the anatomy of Termination 3 using water and air isotopes in the Dome C ice core, East Antarctica

Each glacial – interglacial transition of the Quaternary occurs in a different orbital context leading to various timing for the deglaciation and sequence of high vs low latitudes events. Termination 3, 250 kyears before present (ka), is an unusual deglaciation in the context of the last 9 deglaciations recorded in the old EPICA Dome C (EDC) Antarctic ice core: it exhibits a three-phase sequence, two warming phases separated by a small cooling, the last phase suggesting a particularly rapid temperature increase. We present here new high resolution δ15N and deuterium excess (d-excess) data from the EDC ice core to provide a detailed temperature change estimate during this termination. Then, we combined the δD and δ18O to discuss the relationship between high and low latitude changes through the d-excess. We also provide the high vs low latitude sequence of events over this deglaciation without chronological uncertainty using low latitude ice core proxies. In agreement with previous studies based on speleothem analyses, we show that the first phase of Termination 3 (256–249 ka) is associated with small Heinrich like events linked to changes in ITCZ position, monsoon activity and teleconnections with Antarctica. In a context of minimum Northern Hemisphere insolation, this leads to a rather strong Antarctic warming, as observed in the δ15N record in contrast to the relatively small δD increase. The second warming phase occurs during the rise of the Northern hemisphere insolation, with a large Heinrich like event leading to the characteristic Antarctic warming observed in the δ15N and δD increase as for the more recent terminations.

Vitamin B12 and its binding proteins in milk from cow and buffalo in relation to bioavailability of B12

Milk is an important source of highly bioavailable vitamin B12 (cobalamin) in human nutrition. In most animal products, vitamin B12 is strongly bound to various specific protein carriers. The 2 vitamin B12-specific proteins, predominantly transcobalamin (TC) and haptocorrin (HC), were earlier found in milk from Holstein Friesian cows and in human or sow milk, respectively. As the type of vitamin B12 binders may influence bioavailability of the vitamin, we examined vitamin B12 carriers in pooled milk specimens derived from European and Indian cow and buffalo herds. The total endogenous vitamin B12 concentration was comparable in all milk pools (≈3 nM), but the vitamin carriers varied considerably: TC + caseins in Danish cows, TC + HC in Indian cows and buffaloes, and mainly HC in Italian buffaloes. Danish cow milk contained half as much TC as vitamin B12, and the surplus vitamin was all attached via a single coordination bond to abundantly available histidine residues of casein. The specific binding proteins in Indian cow milk (TC + HC) approximately matched the molar content of vitamin B12. Milk from the 2 buffalo breeds contained more specific binders than vitamin B12, and the surplus proteins included the unsaturated TC ≈ 3 nM (Indian stock), or both TC ≈ 4 nM and HC ≈ 23 nM (Italian stock). The abundant HC of the latter sample bound nearly all endogenous vitamin B12. We tested (in vitro) the transfer of vitamin B12 from milk proteins to human carriers, involved in the intestinal uptake. The bovine TC-vitamin B12 complex rapidly dissociated at pH 2 (time of half reaction, τ1/2 < 1 min, 37°C) and was susceptible to digestion with trypsin + chymotrypsin (pH 7.5). Transfer of vitamin B12 from the precipitated bovine casein (pH 2) to human carriers proceeded with τ1/2 ≈ 7 min (37°C) and τ1/2 ≈ 35 min (20°C). Liberation of vitamin B12 from buffalo HC was hampered because of its pH stability and slow proteolysis. Nutritional availability of vitamin B12 is expected to be high in cow milk (with TC-vitamin B12 and casein-vitamin B12 complexes) but potentially constrained in buffalo milk (with HC-vitamin B12). This especially concerns the Italian buffalo milk, where a high excess of HC was found. We speculate whether the isolated stock of Italian buffalo maintained the ancestral secretion of carriers (HC ≫ vitamin B12, TC ≈ 0), whereas intensive crossbreeding of cows and buffaloes from other regions caused a change to TC ≤ vitamin B12, with low or absent HC. The substitution of HC by less sturdy carriers is apparently more beneficial to human consumers as far as vitamin B12 bioavailability is concerned.

Mechanochemical Synthesis, Accelerated Aging, and Thermodynamic Stability of the Organic Mineral Paceite and Its Cadmium Analogue

We demonstrate the use of ball milling mechanochemistry for rapid, simple, and materials-efficient synthesis of the organic mineral paceite CaCu(OAc)4·6H2O (where OAc– is the acetate ion), composed of coordination polymer chains containing alternating Ca2+ and Cu2+ ions, as well as its cadmium-based analogue CaCd(OAc)4·6H2O. While the synthesis of paceite in aqueous solutions requires a high excess of the copper precursor, mechanochemistry permits the use of stoichiometric amounts of reagents, as well as the use of poorly soluble and readily accessible calcium carbonate or hydroxide reactants. As established by thermochemical measurements, enthalpies of formation of both synthetic paceite and its cadmium analogue relevant to the mechanochemical reactions are highly exothermic. Reactions can also be conducted using accelerated aging, a synthetic technique that mimics geological processes of mineral weathering. Accelerated aging reactivity involving copper(II) acetate monohydrate (hoganite) and calcium carbonate (calcite) provides a potential explanation of how complex organic minerals like paceite could form in a geological environment.